Plant biomass can be a source of fermentable sugar for production of biofuels such as ethanol. A large proportion of plant biomass is cellulose, which is crystallized and densely packed into tight, ordered bundles resistant to water and other solvents. This bundling may help build strong plant cell walls, but strong chemicals, expensive enzymes, and additional energy expenditure is generally needed to break down and separate the bundles and the crystalline cellulose to extract the sugars used to generate biofuels. Incorporation of mannan can alter the structure and assembly of the cellulose so that chemicals and enzymes can break down the cellulose more easily. However, the mechanisms that control mannan synthesis in plant tissues are not understood.